It is well known in the prior railroad arts to provide a track arrangement including a main track and a side track, each comprising two parallel rails. The main track includes a fixed or through rail and a movable, tapering main switch rail having a main switch point, and the side track includes a fixed or side rail and a movable, tapering side switch rail having a side switch point. A switching mechanism facilitates directing of rolling stock through the switch by moving the movable switch rails to either of a first position or a second position.
In the first switch position, the switch directs trains along the main track by keeping the main switch point separated from the main rail (“open”) to allow train wheels to continue along the main rail, in either direction, and keeping the side switch point engaged with the side rail (“closed”) to prevent entry into the side track.
In the second position, the switch connects the main track to the side track by keeping the side switch point spaced apart from the side rail, to facilite entry into or exit from the side track, and the main switch point engaged with the main rail, to divert train wheels from continuing along the main rail, in either direction. (A separate arrangement known in the railroad arts as a “frog” cooperates with the switch to provide a fixed crossing for the second main rail and the second side rail at an appropriate distance from the switch mechanism.)
It is known in the prior art to provide a rotatable switch position indicator of the first and second positions, driven by the switch actuator beside the main track. In the first position, the indicator shows typically a green face to an approaching train engineer, indicating that the switch is set for main track travel; in the second position, the indicator shows typically a yellow face to an engineer, indicating that the switch is set for switching between the main track and the side track. In some known railroad systems, red or white is used for the side rail switch point rather than yellow.
As used herein, train travel through a switch in the direction wherein the through rail and the side rail diverge is defined herein as the first direction of travel, known in the railroad art as a “facing-point” movement. The opposite direction wherein the through and side rails converge is defined herein as the second direction of travel, known in the railroad art as a “trailing-point” movement.
It will be seen that in the first or facing-point direction of travel, on a main track entering a switch, the directing of a train is unambiguous, that is, the switch must be set in either main track or side track mode and the train will follow the switch points (when properly aligned and maintained) on the corresponding tracks accordingly.
It will be obvious that in a properly-functioning switch both points cannot be open at the same time, and that such a condition would lead to derailment of a train. Thus, a serious problem can arise when a train approaches a switch from the second direction in either of the possible trailing-point movements, on either the main track or the side track. If a switch is set for main line travel when a train attempts improperly to enter the main track from the side track, the weight and momentum of the train directed onto the wheel flanges will force open the closed side rail switch point by the width of the flange. This is known in the railroad arts as “running through the switch”. The main rail switch point typically is also displaced by a similar amount. However, the actuation mechanism is not moved, and the switch indicator still indicates that the switch is properly set for main track travel. Thus, the damaged switch is left in a dangerous state wherein neither switch point is fully engaged with its respective rail. The next engineer attempting to go through this switch will find that both the main rail and the side rail pathways are partially open. A train traveling into the switch on the main track in a trailing-point movement may be able to traverse the switch without derailing. Similarly, another train entering the main track from the side track, also in a trailing-point movement, will probably also be able to traverse the damaged switch. However, because the main and side rails diverge, a train traveling into the switch on the main track in a facing-point movement must become derailed.
Of course, a similar problem exists, for the same reasons and with the same results, when a train making a trailing-point movement on the main track enters a switch set for side track switching. In this case, the main rail switch point will be forced open, and a subsequent train making either a trailing-point movement from the side track or a facing-point movement along the main track will be derailed.
All railroads keep running counts of switch derailments, which are very large causes of lost time and profit, and the prestigious industry-wide Harriman Award is earned by the company having the lowest incidence of derailments.
Known in the art as Human Factors Incidents, derailments are held to be the result of human error, and railroad employees are expected to visually determine that a switch is correctly set and passable before a train enters the switch; however, a switch that has been damaged as just described can be very difficult to recognize from the cab of a moving engine, especially at night or under adverse weather conditions, and even if an engineer can see it he may not be able to stop the train in time. Because the industry assumption is that an engineer a) will be guided by the system of visual signals provided, and b) will not intentionally run through an incorrectly set switch, there is great interest in providing means by which engineers and yard personnel can determine visually from either direction, at a substantial distance and with great accuracy under any weather and lighting conditions, whether a switch is properly set and, preferably, whether a switch has been damaged by a previous inadvertent running through.
There are numerous inventions in the prior art intended to alert railroad personnel to this dangerous situation.
Several patents, such as U.S. Pat. No. 5,806,809 and U.S. Pat. No. 6,588,710, employ magnetic proximity sensors in systems to detect whether a switch point is in proper closed relationship to its respective rail. All such inventions require electric power for operation, either line power or solar storage or battery power, which brings a substantial added cost and risk of failure.
U.S. Pat. No. 7,735,784 is directed to a mechanical indicator system employing a rectangular sleeve disposed on a tie between the switch points and housing a reciprocating slide with reflectors, attached between both switch points, selected reflectors being visible through windows in the sleeve to indicate whether the switch points themselves are set in the main track or side track position.
This prior art system can be easily damaged by being struck by low-hanging air hose couplings between rail cars near the track middle. Further, the indicator windows are disposed relatively low between the rails and thus may not be easily seen from a relatively low angle along the track, especially under snowy conditions. Further still, if an associated switch is run through, the indicator system may also be damaged and subsequently present faulty signals which can lead to a derailment.
What is needed in the art is a simple, mechanical indicator assembly that can show unequivocally and accurately the position of a switch point in relation to its cooperating rail.
What is further needed in the art is a system employing a pair of such indicator assemblies mounted on both switch points of a switch to show the actual position of each switch point well in advance of passage by a train.
What is still further needed in the art is a system employing a plurality of such pairs disposed on sequential switches along a main track in a switching yard to show at a glance the settings and conditions of all the switch points. As used herein, “condition” should be taken to mean whether a switch point is correctly or incorrectly positioned with respect to its associated railroad rail.
It is a principal object of the present invention to prevent switch damage by preventing the inadvertent running through of switches set in the incorrect position.
It is a further and larger object of the invention to prevent train derailments at switches.